1. Field of the Invention
The invention relates to a device for voltage supply, in particular in a motor vehicle electrical system, and, more particularly, to a voltage supply device in a motor vehicle electrical system comprising a self-excited, separately-excited or permanently-excited generator delivering a load current and two rectifier arrangements connected downstream of the generator, which deliver a first voltage at a first connector and a second voltage at a second connector.
2. Prior Art
In connection with a motor vehicle electrical system, wherein the supply voltage required for the electrical consumers is generated by means of a generator, it is known that more than one supply voltage should be provided by the generator, so that a dependable, component-specific supply voltage is assured. To this end it is proposed in DE-OS 37 41 242 to embody a separately-excited rotary current generator in such a way that, besides the usual rectified voltage of the vehicle electrical system, rotary current voltages are made available in addition, which are directly used for supplying a window heater. In this case the regulation of the generator is performed with the aid of a voltage regulator which acts on the exciter current. The additional voltage for supplying the heating coils is not rectified, so that losses which unavoidably occur in the course of rectification are prevented.
With some vehicle electrical systems, permanently-excited generators are employed in place of a separately-excited generator. Since an exciter current regulation is not possible with such generators, it is customary to construct the bridge rectifiers downstream of the generator as regulated bridge/-half bridge rectifiers which, for example, comprise semiconductor power switches which are regulated by an associated voltage regulator in such a way that the voltage supplied at the output of the bridge rectifier is approximately constant or is not exceeded, so that it can be used as the voltage of the vehicle electrical system and can be used for charging the vehicle battery or batteries. Such a permanently-excited generator, including the associated regulated bridge rectifier, is known, for example, from DE-OS 38 41 610, however, the generation of a second voltage is not provided in this case.